X-ray-beam generator of high power



' Nbv. 1, 1927. 1,647,479

\ F. 8. SMITH- X-RAY BEAM GENERATOR OF HIGH POWER Original Filed July29.1924 INVENTOR I ATTORNEY Patented Nov. 1, 1927,

- FRANKLIN S. SMITH, BROOKLYN, NEW YORK, ASSIGNQB TO 'II-I'E1PROLDUCTS,PRO

TECTION CORPORATION, OF NEW YQRK,--N. Y., A. (30,RIBORA'IION -01 vDELAWARE;

X-nAY-BEAM GENERATOB or men POWER.

Application filed July 29, 1924, Seria1 No. 728,986. Renewed January 3,192 7;

My invention relates to that class of'X-ray generating apparatus bywhich very intense X-ray'beams are produced. It embodies the hot cathodetype of X-ray tube, and has for its principal object the elimination ofmag netostriction. 1

In standard X-ray tubes of the hot cathode 'jty pe in use at the presenttime, the effect of the magnetic field of the cathode filament heatingcurrent is negligible. For very high powered tubes however, the magneticfield of the filament heating current is able to mhibit entirely theelectron'current between cathode and a'nti-cathode of theX-ray tube. iIn X-ray tubes embodying cathode filaments of certain configuration, forexample a fiat spiral as illustrated in the drawing, the electroncurrent may onlybe inhibited from a part ofthe cathode filament, I

It is also an object of my invention to provide means whereby advantagemay be taken ofthe magnetostriction effect referred to for the purposeof controlling the exciting voltage across the X-ray tube. I

The objects and purposes of mylnventlon will be more fully explained andmore readiilynnderstood by reference to the drawing accompanying andforming a part of th s specification and in which is illustrated sche-LmaticaIly an apparatus of simple form embodying the said invention.

In the drawing,-three circuits, designated 1,2 and 3 are connected tothe-electric current supply mains indicated bysk- Each of these circuitswill be explained separately, and then an eXplanation of the system as awhole will be given.

Circuit 1 comprises a step down transformer designated as 5. .111 serieswith the t: primary of this transformer 1s a' var able creactance 6. Thesecondary of the transformer is connected to the cathode filament 7 ofthe kenotron, designated as a-whole by 8.

the cathode'filamentofthe said ken'otron. Circuit 2-comprises a step uptransformer 9. One end of the secondary is connected to the anode'lO ofthe kenotron 8. The other je'n'd of this winding is connected to oneside of a high voltage permittor 11 thru high resistor 12. The otherside of the permittor is connected to the center the secondary of'"transformer 5, thus completingthe charging J circuit of the sa dpermittor. I In order that 23 and 24. The two pairs of circular 'ringthe drawing may beas simple as is practical and consistent with a propershowing of the invention, only half wave reetification'of the voltageoftransforme'r 9has been illustrated g The purpose ofthis circuitis tounidirectionallycharge the'permittor 11 which stores the exciting energyfor the X ray tube designated as a whole by13. Y I

Ccuit '8' comprises a one to one ratio transformer 1-1 the windings ofwhich are insulated from eachother for' the full voltage of X-ray tubeexcitatioin The secondary of this transformer is 'connecte'd to the synvarrays chronous motor 15 whichis direct connected to generator 16. Thisgenerator isalso direct connected to 'variableflresistor or switchdesignated as a whole by 17. The purpose of generator 16'is tosupply'the heating current for the cathode filament- 18 of the X-raytube 13. This filament is illustrated inthe drawing as a flat spiral onedge.

The variable resistor 17 functions as a synchronous field resistor ofthe-generator 16.

By field control of said generator the heating current thru the cathodefilament 18fof the X-ray tu befis varied, and controlledf The saidvariable resistor, comprises two stationary brushes 19 and 20 which areadapted to contact with the following rotatingmembers :circular;r-ingsectors ligand 22, alsosectors areinsulatedfrom each other in the samemanner in which segments ofa commutator are insulated. Circularringsectors 21 and '22zare connected to each other through high resistor;,andlsectors 23, andQl are connected tofeach other through low re--sistor 26. i I

When the sectors 23 and 24 are inconta'ct with brushes 19 and 20 theresistor 17 is in position ,of minimum resistance In this position themaximum heating current flows throughthe cathode filament 18 from thegenerator16 and magnetostrictionis present; The purpose of this circuitis simply to heat drawing, then the resistor is in'position of maximumresistance. In this position the cathode filament 1s stlll incandescentfrom,

previous heating, but the filament heating current is at a minimum andmagnetostricabove the critical value.

kenotron 8 by the transformer 9. this period of charging, the variableresistor scribed are further interconnected as follows For the purposeof completing the discharge circuit of permittor 11, connection is madefrom junction point 28 to the cathode end of the X-ray tube at 29. Fromthe anti- ;cathode end of the X-ray tube at 30 connection is made tojunction'point 31. This connection is grounded at 32. This completes thedlscharge circult of the permittor 11 through the X-raytube as will beapparent from the drawing.

In the operation of the system the permittor 11 is charged by rectifiedcurrent through During 17 is in position of minimum resistance; the Xraytube then has infinite resistance as magnetostriction is present, thatis, the magnetic field of the filament heating current is When thevariable resistor 17 in in position of maximum re sistance, the positionshown in the drawing, nagnetostriction is absent and the permittordischarges through the X-ray tube.

This cycle is adaptable to continuous repetition. The periodicity andduration of the X-ray beams may be made as desired, through quite widelimits, by simply synchronizing the variable resistor to the desiredperiodicity, and by proportioning the peripheral lengths of the circularring sectors to the desired values. The duration of the X-ray-beam is ofcourse influenced by the constants of the permittor discharge circuit.It will be seen that by my invention I have provided a method andapparatus by the employment of which the lengths of the periods of theproduction and emission of X-ray beams may be controlled, as well as thelengths of the intervals between such periods.

Having thus described my invention what I claim and desire to secure byLetters Pat- 'e'nt is:

1 ode filament, a high voltage permittor, a

filament heating current generator, means for varying the said filamentheating current above and below the critical magnetostric-v tion value.

3. A high powered X-ray beam generator comprising an X-ray tubeembodying a cathode filament a hi h volta e aermittor means b a: a

for charging said permittor, a filament heating current generator, andmeans for increasing the filament heating current to a value source,said means including a source of en-.

orgy for heating said filament and means for periodically increasing thefilament heating on mt to bring about correspondlng periods oiinactivity of said source otX-ray tube exciting energy. o

o. A high powered X-ray beam gen'erato comprising an X-ray tubeembodying a cathode filament, a source of X-ray tube exciting energy, asource of cathode filament heating energy, and means for periodicallyvaryin the cathode filament heating energy above an below the criticalmagnetostriction value.

6. An X-ray beam generator of high power comprising, in combination, anX-ray tube having a cathode filament, a source of high voltage energywhich is adapted to be discharged periodically through the said tube, agenerator for supplying heating current to said filament and a variableresistor in the field of said generator and adapted for periodicallyvarying the current through said filament whereby magnetostrictioncaused by the filament heating currentwithin the tube is periodicallymade ineffective to permit the flow of high 'voltage energy through saidtube;

'i'. In X-ray apparatus, in combination, an X-ray tube having a cathodefilament and a coacting anode; a source of X-ray tube exciting energyconnected across said electrodes; and means for controlling theperiodicity of the discharge of exciting energy through said X-ray tubeand from said source, said means including a source of energy forheating said filament, a resistance for controlling the intensity ofheating current flowing to said filament, and means for periodicallyaffecting said resistance to cause periodic energization of saidfilament cathode at a. current value sufiicient to effectmagnetostriction, therebyto bring about corresponding periods ofinactivity of said X- ray tube. Y I

8. In X-ray apparatus, in combination, an X-ray tube having a cathodefilament and a coacting anode; means forming a source'of relatively highpotential for exciting said X- ray tube; and means for controlling thepe riodicity of excitation of said X-ray tube by said source, said meansincluding a generator for supplying heatlng current to said filament, aresistance in the field circuit ofsaid' generator, and mechanism forperiodically varying the effect ofsaidresistance and adapted to causesaid generator to period ically energize said filament cathode at acurrent value sufiicient to eiiect magnetostriction, therebyto bringabout corresponding periods of inactivity of said X-ray tube.

9. In X-ray apparatus, in'combination, an X-ray tube having a cathodefilament and a c-oactmg anode, means including a source of alternatingcurrent for energizing said X- ray tube, a source of electrical energycapable of energizing said cathode filament at a current valuesufficient to effect magnetostnction and thereby prevent currentdischarge through said tube, and a synchronous device operated from saidsource ofalternating current for effecting periodic energization of saidfilament cathode by said second-mentioned source of. energy.

10. In X-ray apparatus, in combination,

an X-ray tube having a cathode filament and a coacting anode; a sourceof X-ray tube exciting energy connected across said elec-' trodes; andmeans for-controlling the periodicity of the discharge ofexciting energythrough said X-ray tube and: from said source, including means forperiodically energizing said filament cathode at a current value sufficient to. eflect magnetostriction', thereby to bring about correspondingperiods of inactivity of said source of X-ray tube exciting energy.

11. In X-ra-y apparatus, in combination, an X-ray tube having a cathodefilament and a coacting anode, means including a source of alternatingcurrent for energizing said X- ray tube, rotary means for convertingalter: nating current energy from said source to direct current energyand for supplying said filament cathode With the latter, and meansoperated by said-rotary means for period ically causing the latter toenergize said fila-v ment cathode at a current value suflicient toeiiect magnetostriction, thereby to .bring about corresponding periodsof inactivity of

